Electric relay, particularly for purposes of television



' Dec. 3, 1. I K. SCHLESINGER I 2,224,114

ELECTRIC RELAY, PARTICULARLY FOR PURPOSES OF TELEVISION Filed Aug. 5, 19:53

(7n yen for:

Patented Dec. 3, 1940 UNITED STATES PATENT OFFICE ELECTRIC RELAY, PARTICULARLY FOR PURPOSES F TELEVISION Kurt Schlesinger, Berlin, Germany, assignor, by

mesne assignments, to Loewe Radio, Inc., a corporation of New York Application August 5, 1933, Serial No. 683,735

. In Germany August 6, 1932 2 Claims.

My present invention relates to television systems, and has for its objectto provide synchronization at the end of each scanned line and after the scanning of each image. According tomy invention, that section of the receiver which controls the scanning is constructed in such a manner that during the major portion of the time during which line-scanning "and image-scanning takes place, such section will be blocked against the passage of impulses attaining the relatively high voltage employed for synchronizing impulses, and will assume a waiting position only at the end of each line and of each image. .In other words, the voltage employed for l5 the synchronizing impulses is higher than the one of the impulses used for the transmission of image-points, and the apparatus is responsive to such impulses of relatively high voltage only at the end of each line and of each image.- I 20 thus avoid the possibility of accidentally allowing the passage of voltages high enough. to afiect the synchronizing devices, at the wrong moment,

ly given value and duration to be obtained at 5 the receiving end when, proceeding from the transmitter, a certain threshold potential is produced or exceeded. According to the invention, there is employed 'as a relay an electrical tilt- I ing or deflecting arrangement, preferably one .40 having a grid-controlled tilting or deflecting tube, to the grid of which there is applied, in accordance ,with the invention, a constant bias and also the contr "potential.

The constructions illustrated by .the accompanying drawing show an arrangementembodying the invention and effecting the interruption or blocking of the anode current with the aid of a circuit producing free tilting oscillations. 5

In said drawing, Fig. 1 is a diagram illustrating the principle of my invention, while Fig. 2 shows a detail and Fig. 3 a circuit diagram of an apparatus or system embodying said invention.

In Fig. 1, a gas-filled grid glow tube I having a 10 hot cathode 2 (for instance, one heated by a heater filament H), is situated in parallel with a relatively small blocking condenser 3,,which is charged through the medium of a resistance 4 by a D. C. potential source for instance a battery ii. The grid 6 or this glow tube is connected through the medium of a high ohmic resistance 1 with the negative terminal of an additional battery 8, and is, therefore, furnished. with a negative bias of such extent that discharge of the condenser 3 is unable to take place over the glow path, Now it will be clear that any desired potential which is supplied by a remote source of signalling potential 9 and is conducted to therelay over the line ID will be compelled to act on this'glow relay immediately the potential exceeds the ignition surge of the grid potential. The latter is of a definite kind if the potential of the battery 5 and the reciprocal of the tube I are known, and may be adjusted exactly-to within a few tenths of a v olt to any desired selected value by a corresponding choice of the bias 8. If the relay has once been actuated, the condenser 3 will be discharged in a period of time which is proportional to its capacity and the 'in- 'ternal resistance of the path of the glow arc.

This period of time may be made very short, and is an invariable constant of the relay.- If the condenser has been discharged, recharging takes place over the resistance 4 in a period of time 40 which may be regulated by varying the value of 4. If now after completion of the recharging operation the grid potential of 6 is still above the ignition value, a new tilting or deflecting action takes place. potential has again fallen within this period below the surge value, the relay remains in the position of waitinguntil the same is acted upon by a new impulse.

With suitable dimensioning of the condenser 3 it is possible to produce with this connection tilting or deflecting frequencies of up to 200,000 periods and more-= 1! now an ampere-meter or a corresponding recording or indicating instrument A is placed in the charging connection-of If on the other'hand the grid 45' the tilting tube, the same,'for such time as'a control impulse exceeding the surge value. is present at the grid 6, records a'constant current, which corresponds with the median value derived from charging current and discharge current of the tilting or deflecting apparatus. The relay according to the inventior is, therefore, readily capable of use in the form of embodiment according to Fig. 1 for telegraphic transmitters, wireless calling apparatus and the like. Naturally in place of the gas-filled grid glow tubes with hot cathodes it is also possible to employ other glow tubes, more particularly-such as are grid-controlled.

It is also quite readily possible in accordance with the invention to combine the relay with a. tuned receiving circuit, and in this manner to produce automatically recording wireless apparatus of all kinds.

It is, however, particularly convenient to employ the relay according to the invention for synchronising television reception from the contents of the picture. In this connection it is assumed that the high-frequency mixture from the television transmitter includes both image impulses and line impulses, which may be obtained, for example, by the use of a Nipkow disc as scanning means in conjunction with a double edge 4, 5 (Fig. 2) of the image being scannad. This edge may either by darker or lighter than the remainder of the picture. According to the invention, it is particularly convenient. to produce the said edge by additional intense illumination of the edge of the image.

As regards the synchronisation of television images, the connection system illustrated in Fig. 3 has been found to be particularly suitable.

In this connection system there is provided in the first place a glow relay I, such as already described, but combined with a preliminary tube 2 connected in peculiar fashion. The preliminary tube is a high-vacuum rectifier tube, which requires to contain merely two electrodes. The same together with a high ohmic parallelre sistance 3 of suitable size is connected in series with the static (constant) bias of the grid 4 of the glow lamp I, which bias is adjusted once and for all at the grid battery 5. The operation of the preliminary tube arrangement 2, 3 in conjunction with a transmission condenser 6 has already been described in an earlier application, and amounts to a measurement of the peak potential supplied by the transmitter, i. e., the arrangement operates in such fashion that the condenser G'on each occasion endeavours to take up a charge up to the maximum amplitude of the potential proceeding from the transmitter. This charging potential, however, is not quite reached by the condenser, the latter lagging behind the potential all the more the smaller the leakage resistance 3. 0n the'other hand the condenser attains its stationary condition of charge all the more quickly the smaller it is itself and the greater the emissive power of the rectifier tube 2. For this tube there is I preferably selected a modern high-vacuum tube with oxide cathode and indirect, well-insulated heating, a heater element being indicated at H. The result of the action of 2, 3 and 6 is, therefore, that the grid potential of the glow tube l is always smaller to a definite extent than the maximum peak occurring during signalling. If in addition the grid potential is so adjusted at the battery 5 that the excess amount received from the transmitter is sufllcient to actuate the the desired line impulse due to the action of the transmission apparatus. Owing to the stated dimensioning: internal resistance R1 of 2 approximately 100,000 ohms, capacity of Ce approximately cm., i. e., n.e=approximately 10 seconds the amplitude filter is able even during the short transmission line impulse to accommodate and adjust itself to the maximum value thereof. The once adjusted potential remains at the grid of the glow tube I only during the period 16.3=C6.R3. This period is preferably adjusted to approximately half of the line period, which is effected, for example, by means of a resistance R: of a few megohms. In this manner-it is accomplished that occasional strong image content potentials are bloclged off from the tilting or deflecting relay during the recordal of a line, and that the tilting or deflecting relay is sensitive to impulses only at the end of the line. The relay itself after reception of the line impulse at the grid 4 is tilted or deflected with an extremely short period of tilting or deflecting T10- seconds; corresponding at the most with the duration of one image point, which is readily obtained by means of a small condenser 1 of approximately 100 cm. This tilting or deflecting impulse acts on the line 8, at theend of which there is situated a simple frequency filter 9, ID or ll, 12. The very short natural impulse per line does not produce any'appreciable potential parallel to the condenser 10 of approximately 10,000 mm, which is connected in series with the resistance 9 of approximately 100,000 ohms; on the other hand the potential occurs with full force at the terminals of the resistance I! behind a condenser ll of approximately 10,000 cm. At the resistance l2, however, there is connected (as indicated by ZK) the line tilting or defleeting device of the television receiver, which is therefore actuated. This tilting or deflecting device may naturally be either a self-oscillating or a self-suspended tilting or deflecting device assuming a position of waiting until arrival of the line impulse. v

With suitable dimensioningof the charging resistance l3 it is possible in the case of the arrangement as described to perform simultaneous initiation of the image change without requiring lows: Owing to the doubled shuttering of two in Fig. 2 there exists at the transmission end upon a change of image an interval (between signals) of the duration of several lines. Under certain circumstances this interval may be interrupted by providing in the diaphragm a stretched portion or extension 6, which may also consist of a semitransparent material and is employed for maintaining the line synchronism. During this interval in transmission the receiver which, as assumed, .operates if desired with reversah of the phase, takes up a maximum potential for a relatively long period, the gridof the glow tube I accordingly remains positive for a long time, and the relay I, I, I3 performs, therefore, during the any additional apparatus. This occurs as ML whole of this time free tilting or deflecting oscil- 7 reaches the condenser II). From this point, however, an impulse is transmitted (through the connectionindicated at BK) to the image or field or framechange tilting or deflecting apparatus and the change of image caused.

It may be pointed'out that a device such as shown in Fig. 3 may also reproduce without distortion images emanating from television transmitters of that kind in which, owing to certain distribution errors in the transmission disc, the line impulses are not strictly periodical, In particular, owing to the filtering of the amplitude,

which from a chronological aspect takes effect practically only periodically, the disadvantage is avoided that the synchronising signals may be disturbed by the image signals.

What I claim as new and desire to secure by Letters Patent'is:

1. In a television system including a receiver,

ceiver, said anode also being connected to the gri line and image changing circuits, means-rendered operable by synchronizing impulses received by said receiver for controlling said circuits, comprising a triode, a source ofpotential connected to cathode and anode circuits of said triode, a condenser between said source and said triode circuits, said condenser being connected to the input of said line and image-changing circuits for actuating 'them upon discharge thereof through said triode, the grid of said triode being normally negatively biased to prevent the discharge of said condenser through said triode, said grid being connected to the output of said receiver for allowing said condenser to discharge through said tube throughout the period when said grid is rendered positive by said synchronizing impulses.

2. In a television system as claimed in claim 1, including a level maintaining device for blocking off impulses from said grid during intermissions between said synchronizing signals, said level maintaining device comprising a thermionic diode shunted by a leak resistance, another condenser, the anode oisaid diode being connected by said other condenser to the output of said reof said triode, the cathode of said diode having a negative bias.

- KURT. SCHLESINGER. 

